Best plants for Boulder gardens
Boulder gardens sit at about 5,430 ft in USDA zone 6a, with heavy alkaline clay, roughly 18 to 20 inches of precipitation a year, and a last spring frost around May 5. The defining challenges here are fierce chinook winds, deer pressure on the foothills edge, and an established emerald ash borer infestation, so the plants below lean wind-tough, deer-resistant, and water-wise.
Last updated 2026-05-30
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Boulder growing conditions
- USDA hardiness zone
- 6a (cooler 5b at higher elevations west)
- Elevation
- 5,430 ft
- Avg. annual precipitation
- ~18 to 20 in
- Soil
- heavy alkaline clay; rocky on the foothills west side
- Avg. last spring frost
- ~May 5
- Avg. first fall frost
- early October
- Growing season
- ~144 days
Boulder is the warmest of the north Front Range towns thanks to its foothills/urban setting, but it pays for that with the region's most punishing downslope chinook winds and a hard western edge where cold air drains off the mountains. West-side and Chautauqua-area gardens run cooler and windier than east Boulder and Gunbarrel.
What's challenging in Boulder
Emerald ash borer is established here
Boulder was the first confirmed emerald ash borer (EAB) site in Colorado, detected in the city in September 2013, and the beetle is now established across Boulder County (Boulder, Gunbarrel, Longmont, Lafayette, Superior, Lyons). If you have an ash tree (genus Fraxinus), talk to a certified arborist about treatment versus replacement; do not plant new ash. The recommended trees below are diverse, non-ash species suited to the Front Range. (source)
Chinook winds dry plants out
Boulder routinely sees downslope chinook winds of 60 to 70+ mph (gusts over 100 mph have been recorded near NCAR), peaking December to May. Wind desiccates foliage and stresses new transplants, so wind-tolerant species and good establishment watering matter more here than almost anywhere on the Front Range. (source)
Foothills deer browse
West Boulder and the foothills interface see heavy deer pressure. No plant is truly deer-proof, so the lists below rank plants rated deer resistant higher, and those are far less likely to be browsed.
Top trees for Boulder
Ranked for Boulder's drying wind, deer browse, hail and low water use.
One-seed JuniperJuniperus monosperma10 to 20 ftlow waterColorado nativeUSDA 3 to 8
Pinyon PinePinus edulis15 to 30 ftlow to medium waterColorado nativeUSDA 4 to 8
Ponderosa PinePinus ponderosa60 to 100 ftlow to medium waterColorado nativeUSDA 3 to 7
Thornless Common Honeylocust (IMPERIAL®)Gleditsia triacanthos40 to 50 ftlow to medium waterUSDA 3 to 9- Thornless Common Honeylocust (NORTHERN ACCLAIM®)Gleditsia triacanthos30 to 45 ftlow to medium waterUSDA 3 to 9
Rocky Mountain Douglas firPseudotsuga menziesii var. glauca40 to 80 ftmedium waterColorado nativeUSDA 4 to 6
Rocky Mountain Juniper (species)Juniperus scopulorum15 to 30 ftlow waterColorado nativeUSDA 3 to 8
Arizona CypressHesperocyparis arizonica30 to 50 ftlow waterUSDA 7 to 10
Top shrubs for Boulder
Ranked for Boulder's drying wind, deer browse, hail and low water use.
Apache plumeFallugia paradoxa4 to 6 ftlow waterColorado nativeUSDA 4 to 9
Big sagebrushArtemisia tridentata3 to 8 ftlow waterColorado nativeUSDA 3 to 9
Common juniperJuniperus communis2 to 4 ftlow waterColorado nativeUSDA 2 to 7
Curlleaf mountain mahoganyCercocarpus ledifolius10 to 20 ftlow waterColorado nativeUSDA 3 to 8
FernbushChamaebatiaria millefolium4 to 6 ftlow waterColorado nativeUSDA 4 to 8
LeadplantAmorpha canescens2 to 4 ftlow waterColorado nativeUSDA 4 to 9
Mountain mahoganyCercocarpus montanus6 to 12 ftlow waterColorado nativeUSDA 3 to 8
New Mexico privetForestiera neomexicana6 to 12 ftlow waterColorado nativeUSDA 4 to 8
Top perennials for Boulder
Ranked for Boulder's drying wind, deer browse, hail and low water use.
Bee Balm/HorsemintMonarda fistulosa24 inlow waterColorado nativeUSDA 3 to 9
Black-eyed SusanRudbeckia hirta24 inlow waterColorado nativeUSDA 3 to 9
BlanketflowerGaillardia aristata12 inlow waterColorado nativeUSDA 3 to 10
Blue FlaxLinum lewisii18 inlow waterColorado nativeUSDA 4 to 9
Butterfly MilkweedAsclepias tuberosa18 inlow waterColorado nativeUSDA 3 to 9
Chocolate FlowerBerlandiera lyrata18 inlow waterColorado nativeUSDA 4 to 9
Common YarrowAchillea millefolium18 inlow waterColorado nativeUSDA 3 to 9
Desert Four O’ClockMirabilis multiflora18 inlow waterColorado nativeUSDA 4 to 9
Top groundcover for Boulder
Ranked for Boulder's drying wind, deer browse, hail and low water use.
Mat penstemonPenstemon caespitosus2 to 4 inlow waterColorado nativeUSDA 3 to 8
Small-leaf pussytoesAntennaria parvifolia2 to 5 inlow waterColorado nativeUSDA 3 to 8
Sulfur buckwheatEriogonum umbellatum6 to 12 inlow waterColorado nativeUSDA 4 to 8- Serbian yarrowAchillea serbica4 to 6 inlow waterUSDA 3 to 9
Silverheels horehoundMarrubium rotundifolium6 to 12 inlow waterUSDA 4 to 8
Turquoise Tails blue sedumSedum sediforme4 to 8 inlow waterUSDA 3 to 9
Blue fescueFestuca glauca6 to 10 inlow to medium waterUSDA 4 to 8- CRYSTAL RIVER® veronicaVeronica 'Reavis'2 to 4 inlow to medium waterUSDA 3 to 8
Rebates & water rules in Boulder
City of Boulder water customers replacing at least 200 sq ft of turf. Resource Central's 2026 program is full and closed; it says applications reopen in spring 2027.
Watering rules: Front Range norm: no daytime watering 10 a.m. to 6 p.m.; check the city for current restriction stage and assigned days. current rules →
What's open right now across the Front Range, with dates and the rules that trip people up: lawn replacement rebates by city →
Statewide: new Colorado turf rules (SB24-005/HB25-1113) limit nonfunctional turf in new development, and HOAs can't ban xeriscaping (SB23-178). Read the statewide rules →
Local resources near Boulder
- Extension
Boulder County CSU Extension, Master Gardener help desk, Free, science-based plant, pest, and soil advice from CSU-trained Master Gardeners. - Nursery
Harlequin's Gardens, Long-running Boulder nursery specializing in pesticide-free natives and xeric plants. - Native plant society
Colorado Native Plant Society, Boulder Chapter, Local native-plant walks, talks, and plant sales.
When to plant in Boulder
Plant trees and shrubs in spring (April to May) or early fall so roots establish before chinook season; protect new transplants from drying winds. Wait until mid-to-late May for tender annuals. Boulder's chinook winds make spring timing fickle. Let soil warm before setting out heat-lovers.
Video
Video PlantTalk Colorado: planting & tree-care videos (CSU Extension)
Boulder gardening FAQ
- What hardiness zone is Boulder, Colorado?
- Boulder is USDA zone 6a, with cooler 5b pockets at higher elevations on the west side.
- When is the last frost in Boulder?
- The average last spring frost is around May 5, though late frosts into mid-May happen. Wait for warm soil before planting tender annuals.
- Should I plant an ash tree in Boulder?
- No. Emerald ash borer is established in Boulder County; plant a diverse, non-ash species instead and consult a certified arborist about any existing ash.
Targeted guides for Boulder
Plan your garden
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